Alloy of azotized character



Patented June 28,1932

UNITED ra l-Es ATENT oFrica' RICHARD R. WALTER,- OF 'S'I'ABNBEBG, GEMANYALLOY or azorrzsn cnaaacran No Drawing. Application filed September so,1929, Serial in. $94,136, an in Germany Au ust- 5, 1929.

My invention pertains to sintered alloys of the class which include acarbide, a nitride or a carbonitride of a metal or metalsof the chromiumgroup and which-while hard are also tough bylreason of the inclusion ofaux- .iliary metal or, metals either from one or more groups and moreparticularly pertains to an alloy containing azotized, nitride'd ornitrified metal from either one, or metals from IOboth', of the iron andchromium groups.

It is known that hard alloys principally consisting of carbides andnitrides or car- 'bonitrides of the chromium group are oftenmanufactured by mixing with lower melting 19 metals ofeither or both ofthe iron and chromium groups, pressing of the p0wd'eredin gredient's andthensubjecting them to a sintering process. z e

The auxiliary metals are purposed to cause the individual particles ofthe main mass for-example, the carbidesetc. to stick to'%ether as onetenacious piece uch alloys find principal use as tools or arts which aresubjecxged to severe wear. owever the auxiliary etals, which are in"every case, softer than the material of the main mass, as for example,the carbides, nitrides etc. reduce the tenaciousness of the alloysagainst wear or their resistance to wear and it is for, that reason thatthe ainount of auxiliary metal to be added is restricted.

It was discovered that this harmful effectof the auxiliary metals can heavoided and their resistance to wear noticeably enhanced if, one employsthem-in the formof azotides i. e. as metals combined with nitrogen. Theauxiliary metals of the iron group (Fe,Mn, Ni, Co) or these incombination with metals of the chromium group (Cr W, Mo, U) according tothis invention first subjected to azoti'za'tion (in.a manner exceptingtlmgsten means of dissociated nitrogen while in their powdered conditionand before their mixture with the elements to be sintered. In the caseof ,tungsten'the azotization requires also the simultaneous presence ofhydrocarbons.

I have made the discovery that the nitrification is consummated withmar'kdly greater facility and is also possible with by itself previouslyknown and suitably by such mot alswhich heretofore resisted it,"especially with all metals of the iron group (iron, manganese, cobaltand nickel) and of the chromium group (chromium, tungsten, molybdenumand uranium), when the nitrification proceeding follows a superficialcarburization or when thecarburization occurs simul taneously with thenitrification.

Because the melting temperature generally rises in proportion as thenitrogen content increases, one does not carry the azotization 'so faras to make the subsequent sintering process more difiicult.

It was discovered for instance, that even a content of five-hundredthper cent of nitrogen (.05% N) produces a considerable in crease in thetenacity against wear. Expediently one should not use much over one percent nitrogen (1% N), even thou h a still greater proportion can beusefu if one reckons with the consequential increase in the temperaturerequired to sinter.

It was also discovered that the a'zotization of the aun'liary metalsneed not occur before their mixture with the primary elements, but 75can also occur with equal successsimultaneously during the sinteringprocedure. The principalelements llke carbides or nitrides orcarbonitrides are adequately mixedwith the auxiliary metals, as forexample, iron, nickel or cobalt and tungsten or others in a powderedstate, pressed to formed pieces. R and these sintered in the usualmanner. The azotizatinn hen ensues during the sinterin process byassfige thereover of dissociate nitrogen" gas or ammonia (NH- gas I orelse while one conducts the hydrogen (employed as a protecting gas)through an-am-f moniacal solution whereit becomes chargedwith ammonia(NH gas. The formpressed 'ecesto be sintered, in consequence of their 1"sue porosity, exe'rt a considerable ca efi'ect to gases and thenitrogen] fiuses through the'entire cross section ofthe bodies. {As anexample conformable to the inventionthe followin alloy is specified':-seventy percent tungsten carbide, fifteen percent (15%) azotizedtungsten, ten per-.

cent (10%) azotizedcobalt, three percent w (3%) ,azotized chromium.

'1 claim 5- 7 1. An alloy comprising principally a powtiered, pressedand sintered carbonaceous tungsten compound together with at least one r5 homogeneously mixed azotized auxiliary metal of the iron or chromiumgroup.

2. An alloy comprising p-rincipallya powtiered, pressed and sinteredcarbonaceous tungsten compound together with homogenel0 ously mixedazotized auxiliary metal of both the iron and-chromium groups.

3, An alloy according to claim 1, in which a mixture of azotizedtungsten carbide and of an azotized metal of the chromium group 1 is emloyed. p p

4; alloy according to claim 1, in which is employed as auxiliary metal amixture of azotized metal of the iron group and azotized metals of thechromium group. 2 5. An alloy comprising over fifty per cent of acarbide of tungsten and azotized auxiliary metals comprising one of thechromium group ofhigher melting temperature than said carbide and one ofthe iron grou of 25 lower melting temperature thanthe mefiingtemperature of said carbide, the whole being inpowde red, compressed andsintered form.-

6. An" alloy is comprising over fifty (50%) per cent 'of a carbonaceouscompound of Q metal ofthe chromium group and the remainder azotizedtungsten, azotized cobalt and azotized chromium.

RICHARD RWALTER.

